Have you ever used Google’s photo search feature? Type in ‘cat’ and it will pretty reliably bring up any cats in your photo collection. It’s not perfect – it mistakes Land Rovers for cats some of the time – but it’s getting better all the time. And that is the point of machine learning. Among much else, machine learning, a subset of which is called deep learning, now powers Google photo search, speech recognition on Android, and video recommendations on YouTube.